12v negative earth

[bastion]

I am wanting to fit a 12v car radio, but my problem is locating the earthing point. Is it just anywhere on the hull or would there be a dedicated point?

I currently have 12 v lights pumps etc and 240v run through a Victron Multi-plus. I have tried looking through old posts but have got confused by talk of shared earths or not.

Thanks in advance, Bastion

[Keeping Up]

Normally on a boat unlike a car the negative connection to each appliance, be it a light the water pump or the radio, should be by a wire (usually a black one). On a car the metalwork of the car is used instead because it's cheaper but on a boat that can cause corrosion of the hull which sinks the boat. If you're fitting a new radio you should fit a red positive supply and a black negative wire to it from the main fuseboard or distribution box, you can use twin cable to make that easier. It should be fairly thick wire because the peak current is fairly high, ours is 6 sq mm.

 

The need to isolate the braid of the aerial connection from the hull is a topic for later discussion.

[bastion]

I can only find the source of the red cables cannot find any black cables in my electric cupboard. The red cables come from the switch panel, 11 switches marked up light, pumps etc. Was hoping to get an adapter and use the existing co-axial aerial

Edited January 16, 2015 by bastion

[bastion]

Thanks for your advice. Think I have found the black negatives, from their position I thought that they were on the 240v circuit.

[Tom Richmond]

The black negative wires usually all connect together on what's called a "bus bar" its a metal strip with several threaded studs which the individual cables (with ring crimps on their ends) bolt on to. It is often slightly removed from the positive (red) connectors, as you do not need to access it to change fuses, nor does it need to be in any particular place for access to switches.

[ditchcrawler]

Thanks for your advice. Think I have found the black negatives, from their position I thought that they were on the 240v circuit.

STOP If you can't differentiate between you 240 volt circuits don't touch your electrics

[bastion]

STOP If you can't differentiate between you 240 volt circuits don't touch your electrics

Have traced the circuits. The confusing bit was that the 12v negative busbar is immediately above the 240v change-over box, not the best of layout design.

Thanks for the help.